This application represents a Competitive Revision to grant R01ES015384, in response to the Notice Number (NOT-OD-09-058) and Notice Title: NIH Announces the Availability of Recovery Act funds for Competitive Revision Applications. In the parent grant, we are analyzing the function and enzymatic activity of the enzyme, cytochrome P450 2S1 (CYP2S1). In this revision, "CYP2S1 and Asthma", we will now extend these studies to investigate the role of CYP2S1 in the initiation and progression of asthma. Several of our (unpublished) observations suggest that this enzyme plays a role in this disease, and in particular, may function as a counter- regulatory mechanism to diminish the severity of individual asthmatic episodes. These observations include the following. (a) Cyp2s1 is highly expressed in mouse (and human) lung. (b) Hypoxia upregulates Cyp2s1 expression in mouse and human cell lines and in mouse lung in a process mediated by Hypoxia Inducible Factor (HIF). (c) HIF is required for the asthma-like response in a mouse model of asthma. (d) Cyp2s1 is upregulated in mouse lung during the asthma-like response. (e) Cyp2s1 is very active in the degradation of eicosanoids, many of which are known to be intimately involved in the initiation and progression of asthma. Specific Aim 1 will test our hypothesis that Cyp2s1 activity diminishes the asthmatic response. To this end, a newly developed knockout mouse for Cyp2s1 will be utilized to ascertain whether loss of Cyp2s1 activity enhances the manifestations of asthma-like symptoms in both the acute and chronic phases. Specific Aim 2 will test our hypothesis that the profile of eicosanoids differs between Cyp2s1 knockout and wild-type mice during the asthma-like response, thus providing a potential explanation for the enhanced asthma-like response in the former. To this end, (a) the metabolism of relevant eicosanoids by purified mouse Cyp2s1 and by microsomes from both types of the above mice treated or untreated with the asthma-inducing protocol, will be examined, and (b) the profiles of eicosanoids in lungs, bronchiolar lavage fluid (BAL) and sera from these mice will be determined. Specific Aim 2 will thereby identify eicosanoids whose concentrations in mouse tissues correlate with the severity of the asthma-like response, and also determine whether these eicosanoids are substrates of Cyp2s1, thus identifying the particular eicosanoid(s) that are likely responsible for mediating the protective effect of Cyp2s1 towards the asthma-like response. Our studies will potentially point to a novel target for asthma therapy, namely CYP2S1. Our previous studies suggest that certain natural compounds found in vegetables can upregulate Cyp2s1. These compounds therefore may represent potential novel therapeutics for asthma. PUBLIC HEALTH RELEVANCE: These studies will provide mechanistic insight into an important environmental disease - asthma. Furthermore, they promise to identify the enzyme CYP2S1 as a novel molecular target for agents for the treatment, amelioration or prevention of asthma. Such agents could include certain natural chemicals that impact the activity of CYP2S1, which are found in vegetables.